Question

Two waves of equal amplitude A, and equal frequency travel in the same direction in a medium. The amplitude of the resultant wave is.

(a) 0

(b) A

(c) 2A

(d) between 0 and 2A.

Answer 1

(d) between 0 and 2A.

EXPLANATION: 

The amplitude of the resultant wave depends on the phase difference between the two waves. If the phase difference is zero then the resultant amplitude is maximum = A+A = 2A. But if the phase difference is π, then the resultant amplitude is minimum =A-A = 0. So the amplitude of the resultant wave is between 0 and 2A depending on the phase difference.